B&M 20301 Transmission Speedometer Port Plug

Fits GM TH400

PART# 20301

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$31.00   Suggested Retail
$27.95   Your Price
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Does NOT fit B.O.P (Buick, Oldsmobile & Pontiac) TH-400


B&M Racing & Performance brings you this billet aluminum speedometer port block-off plug that fits GM TH400 transmissions. This plug is used to block the mechanical speedometer gear port when upgrading to an electronic speedometer and includes a replaceable Buna-N-rubber o-ring. It features a black Mil-Spec anodized finish for long lasting good looks, even in harsh conditions. Comes with hardware and instructions for a quick and easy installation.


  • Billet Aluminum Construction with Engraved B&M Logo
  • Protects Your Transmission from Contaminants during use or storage
  • Replaceable O-ring seal for leak prevention and simple maintenance
  • Perfect for Electronic Speedometer Conversions
  • Mil-Spec Black Anodized Finish for long lasting good looks
  • Includes Stainless Steel Hardware for Superior Corrosion Resistance

Product Attributes

Emission Code5
Product TypeSpeedometer Port Plugs
Part Number20301



This part is legal for sale or use on Emissions Controlled Vehicles, Uncontrolled (Non-Emissions Controlled) Vehicles, and Racing Use Only Vehicles because it does not affect vehicle emissions and is not covered by emissions regulations.

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    *Free Shipping & Handling only offered to the contiguous US on orders over $100, excludes clearance parts and oversized packages.

    Some parts are not legal for use in California or other states with similar regulations.